class Compiler{
    constructor(vm){
        this.el = vm.$el
        this.vm = vm
        this.compile(this.el)
    }
    //编译模板 处理文本节点和元素节点
    compile(el){
        //遍历el的所有节点
        let childNodes = el.childNodes
        Array.from(childNodes).forEach(node=>{
            if(this.isTextNode(node)){
                this.compileText(node)
            }else if(this.isElementNode(node)){
                this.compileElement(node)
            }

            //判断node节点 是否有子节点 如果有子节点 要递归调用compile
            if(node.childNodes && node.childNodes.length){
                this.compile(node)
            }
        })
    }

    //编译元素节点 处理指令
    compileElement(node ){
        //console.log(node.attributes)
        //遍历所有的属性节点
        Array.from(node.attributes).forEach(attr=>{
            let attrName = attr.name
            if(this.isDirective(attrName)){
                //v-text --> text
                attrName = attrName.substr(2)
                let key = attr.value
                if(!this.isEventDirective(attrName)){
                    this.update(node,key,attrName)
                }else{
                    this.updateEvent(node,key,attrName)
                }
            }
        })
        //判断是否是指令
    }

    update(node,key,attrName ){
        let updateFn = this[attrName + 'Updater']
        updateFn && updateFn.call(this,node,this.vm[key],key)
    }

    updateEvent(node,method,attrName){
        let event = attrName.split(":")[1];
        node.addEventListener(event,(e)=>{
            if(this.vm.$options.methods[method]){
                this.vm.$options.methods[method](e)
                this.vm.$options.methods[method].call(this.vm,e)
            }
        })
        console.log(node,method,attrName,'event',event)
    }

    // 处理 v-text 指令
    textUpdater(node, value,key){
        node.textContent = value
        new Watcher(this.vm,key,(newValue)=>{
            node.textContent = newValue
        })
    }

    //v-model
    modelUpdater (node,value,key){
        node.value = value
        new Watcher(this.vm,key,(newValue)=>{
            node.value = newValue
        })
        //双向绑定
        node.addEventListener('input',()=>{
            this.vm[key] = node.value
        })
    }

    htmlUpdater (node,value,key) {
        node.innerHTML = value
        new Watcher(this.vm,key,(newValue)=>{
            node.innerHTML = newValue
        })
    }


    //编译文本节点，处理差值表达式
    compileText(node) {
        let reg = /\{\{(.+?)\}\}/
        let value = node.textContent
        if(reg.test(value)){
            let key = RegExp.$1.trim()
            node.textContent = value.replace(reg,this.vm[key])

            //创建watcher对象
            new Watcher(this.vm,key,(newValue)=>{
                //数据改变的时候这里就能被调用了
                node.textContent = newValue
            })

        }
    }
    //判断元素属性是否指令
    isDirective(attrName) {
        return attrName.startsWith('v-')
    }

    //判断节点是否是文本节点
    isTextNode(node){
        return node.nodeType === 3
    }
    //判断节点是否是元素节点
    isElementNode(node) {
        return node.nodeType === 1
    }

    //判断是否事件指令
    isEventDirective(attrName){
        return /\w+:\w+/.test(attrName);
    }
}